Could milk get you mad cow disease?

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By Jimmy Downs
 
Chronic wasting disease

Monday Oct 29, 2012 (foodconsumer.org) --Chronic wasting disease, a brain wasting disease in deer was confirmed on Oct. 8 in a captive 3.5-year old doe that died on Oct 4. The deer was kept in a facility in New Oxford, Adams county in Pennsylvania.  

The case has prompted the Pennsylvania Game Commission to run a check station in counties of concern to contain the case of chronic wasting disease, which is known to spread through the animals' saliva, urine and faces.

Chronic wasting disease (CWD) is fatal in deer, elk, and moose and the infectious agents commonly called prions can survive in soil for many years.
 
Media reports say there is no evidence to suggest the chronic wasting disease can spread from deer to humans, which does not mean that eating deer meat is safe.  The risk of the transmission of chronic wasting disease has not been thoroughly assessed and caution needs to be exercised to avoid contracting a possible fetal disease.

A study by the Centers for Disease Control and Prevention suggests that "[m]ore epidemiologic and laboratory studies are needed to monitor the possibility of such transmissions." 

And the epidemiological study further concludes "[a]s a precaution, hunters should avoid eating deer and elk tissues known to harbor the CWD agent (e.g., brain, spinal cord, eyes, spleen, tonsils, lymph nodes) from areas where CWD has been identified."

Other studies, reported below suggest that even meat and milk commonly believed to be safe to eat or drink may pose a risk.

Milk from cows with mad cow disease may spread the disease?

Mad cow disease is a prion disease or brain wasting disease.  Prions are misfolded proteins that are infectious and naturally transmitted, causing fetal neurological diseases in humans and animals.

A study in Journal of Virology reported by C. Ligios of Istituto Zooprofilattico Sperimentale della Sardegna in Sassari, Italy and colleagues suggests that prions can get into milk and drinkers may get infected by drinking milk from infectious animals and develop brain wasting disease like chronic wasting disease in deer, scrapie in sheep, variant Creutzfeldt-Jokob Disease in humans, and mad cow disease in cows.

The study showed that sheep with scrapie and lentiviral mastitis secreted prions into their milk and affected 90 percent of naive suckling lams.  

The finding may provide one explanation as to how brain wasting disease gets transmitted from animal to animal.  But could this finding also suggest one possible route for humans to acquire human version of mad cow disease through drinking milk from animals - sheep, goats and cows with brain wasting disease?

Prions are extremely stable.  The pasteurization process applied for sterilization of milk could in no way kill infectious prions.  It has been known that eating meat from cows infected with mad cow disease can cause human version of mad cow disease, variant Creutzfeldt-Jokob Disease.

To prevent mad cow disease from entering humans, meat with bones and certain tissue like brain tissue is not allowed to be sold for human consumption in the U.S. because these tissues from sick animals are found high in prions.  

A study of humans with variant Creutzfeldt-Jakob disease (vCJD)  has found that abnormal prion proteins, which are responsible for the disease, can spread to all organs and tissues through the circulating system and other routes.

The study was conducted by Dr. I Ramasamy at Department of Health in Canberra, Australia and colleagues and published in the Lancet Infectious Diseases in 2003.

Milk has never been considered a possible route for the transmission of mad cow disease from animals to humans.  But these studies hint that drinking milk from cows infected with mad cow disease can get drinkers variant Creutzfeldt-Jakob disease, human version of mad cow disease.

In Japan, every cow before hitting to the market is tested for mad cow disease.  In the U.S., beef is not allowed to be tested by private organizations for mad cow disease.

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